The effect of pump-wave misalignment on the oscillation spectra of a semilinear photorefractive oscillator is studied numerically and compared with the results of experiments performed with BaTiO3:Co and KNbO3:Ag,Fe crystals.

High contrast optical bistability is found experimentally in the pump-ratio dependences of the output intensity of a semilinear photorefractive coherent oscillator with two counterpropagating pump waves. The data are in qualitative agreement with the results of calculation.

We present a theoretical analysis, analytical and numerical, ofthe oscillation regimes for the semi-linear photorefractiveoscillator beyond the instability threshold. This analysisincludes the limiting cases of dominating transmission andreflection gratings as well as the cases of spontaneous violationof the frequency degeneracy between the oscillation and pumpwaves.

A general analysis of the threshold behavior for the photorefractive semi-linear oscillator is performed within the linear approximation on the basis of the classical wave-coupling model. This analysis shows that the well known particular results on the frequency degenerate oscillation are valid only within a restricted range of the external parameters. The theory specifies the conditions for onset and properties of the frequency non-degenerate oscillations, including the necessary values of the coupling strength, pump intensity ratio, the increments of the instability, and the frequency splits. Important generalizations of the basic model are considered.

The self-development of a strong reflection grating in a BaTiO3 sample illuminated with two mutually incoherent counter-propagating light waves is reported. The two transmitted waves diffracted from this grating become partially mutually coherent.

The sequence of optical phase transitions is considered for a photorefractive coherent oscillator with a conventional mirror and a four-wave mixing phase conjugate mirror. Analogous to phase transitions in solids, the phase diagrams are constructed and defined qualitatively as different states of a whole system (light-induced scattering below the threshold of oscillation, single-frequency oscillation, two-frequency oscillation, and multimode mirrorless oscillation). The attempt of experimental mapping of a phase diagram is presented for a coherent oscillator with Co-doped BaTiO 3 .

The saturation intensity, oscillation spectrum, and temporal dynamics of oscillation are studied for a semilinear coherent oscillator with two counterpropagating pump waves and a photorefractive crystal with dominating reflection gratings. The instability of the single-frequency oscillation spectrum is revealed, similar to that known for an oscillator with dominating transmission gratings. The experimental manifestation of this transition in the output characteristics of the oscillator is favourably compared with numerical calculations.

We present a self-pumped phase conjugator originated by self-bending of the incident beam at λ = 515 nm in a BaTiO3:Rh waveguide elaborated by three successive He+ ion implantations. Phase conjugate reflectivity reached is 28 %.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text P. Mathey, P. Marquez, P. Moretti, and D. Rytz, "Self-bending of the light in a photorefractive planar waveguide fabricated with He+ implanted BaTiO3:Rh," in Nonlinear Guided Waves and Their Applications, A. Sawchuk, ed., Vol. 80 of OSA Trends in Optics and Photonics (Optical Society of America, 2002), paper NLMD39. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

We demonstrate experimentally an optical parametric oscillator constructed in a waveguide induced by a photorefractive spatial soliton and show that the pumping threshold is reduced considerably.

La dynamique et l'etat stationnaire du faisceau issu d'une cavite oscillante comprenant un cristal non-lineaire de titanate de baryum utilise en tant que miroir a conjugaison de phase sont etudies. Le parametre du systeme etant le gain du milieu non-lineaire, les dependances de l'intensite de l'oscillation et de l'inverse du temps de reponse sont similaires aux lois de Curie en physique du solide.

The transition of the single-frequency oscillation of a semilinear photorefractive coherent oscillator for sufficiently large coupling strengths into two-frequency oscillation is predicted and is observed experimentally. The critical value of the coupling strength at which the bifurcation occurs is a function of pump intensity ratio and cavity losses. The supercritical bifurcation in the oscillation spectrum is analogous to the second-order phase transition.

For the very first time to our knowledge, guided waves at 854 nm are observed in a BaTiO3:Rh waveguide fabricated by the technique of ion-beam implantation. The photorefractive interaction between two guided modes is demonstrated and characterized. The experiments revealed that the gain direction is reversed in the guiding layer in comparison with that in the bulk. A maximum gain of 24 cm(-1) is achieved. (C) 2001 Optical Society of America.

The temperature distribution in a parallelepipedic crystal irradiated with a Gaussian repartition of light is calculated by solving the three-dimensional heat equation and taking into account the losses through the sides of the samples. The theoretical and experimental maps of temperature are satisfactorily compared. For barium titanate crystals, the resistance to intense cw laser (25.7 kW/mm(2) at 514.5 nm) and to Nd:YAG pulsed laser (peak power of 9.2 MW at 532 nm) is investigated. The defects induced by the irradiation are analysed. Under pulsed illumination, the damage threshold is found to be 0.54 GW/cm(2) in a nominally undoped BaTiO3 and 0.44 GW/cm(2) in a rhodium-cobalt doped BaTiO3 crystal.

Summary form only given. At the infrared wavelengths, a few studies have been dedicated to the photorefractive properties of waveguides fabricated with oxide ferroelectric crystals. For the first time, a waveguide is fabricated by the technique of ion-beam implantation in a BaTiO/sub 3/:Rh substrate. The characteristics of the photorefractive effect are studied via two-beam coupling experiments.

Summary form only given. In ferroelectric crystals like KNbO/sub 3/, LiNbO/sub 3/, BaTiO/sub 3/, SBN the wave mixing performances based on the photorefractive effect are strongly affected by the polydomain feature of the material. To obtain high reflectivities, the monodomain feature is strongly desirable inside the volume of the crystal as well as at its faces. This work presents results on the detection and the shape of antiparallel ferroelectric domains at the c-faces of a rhodium doped BaTiO/sub 3/ crystal.

Using electron paramagnetic resonance, optical absorption, and fast spectroscopy of light-induced absorption changes, it is shown that codoping BaTiO3:Rh with NaBa acceptors raises the charge state of Rh3+ to Rh4+. Subsequent oxidation under high oxygen pressures can lower the Fermi level to Rh4+/5+, leading to increased infrared absorption. The light-induced charge transfer in such specimens is characterised by “one center” behaviour.